Chemical treatment of semiconductor substrates

ABSTRACT

A method is disclosed for removing liquids from a semiconductor substrate by contacting the liquid on the substrate with a liquid which attracts the liquid on the substrate, separating the liquids from the substrate, and inducing a phase transition in a layer on the substrate. In particular, the method is applicable to removing water from a water-containing layer on the substrate by contacting the layer with a hygroscopic liquid. Trenches on a substrate can be isolated by filling the trenches with a water-containing gel formed by reacting silane and hydrogen peroxide. The gel is contacted with sulfuric acid to remove a portion of the water from the gel before annealing to form silica in the trenches. Unlike filled trenches formed by conventional technology, there are no voids in the bottom of the trenches. The method is also applicable to forming dielectric layers which cover metal lines, low-dielectric layers, and interlayer dielectric layers. The liquid may be applied to the substrate by chemical vapor deposition or by spin-applying.

REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.10/027,519, filed Dec. 20, 2001 which is a continuation of U.S.application Ser. No. 09/388,570, filed Sep. 2, 1999 issued on May 28,2002 as U.S. Pat. No. 6,395,647.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of treating semiconductorsubstrates by exposing the substrate to a hygroscopic liquid. Thetreatment minimizes the formation of voids in the fabricatedsemiconductor.

2. Description of the Related Art

During the fabrication of semiconductors and integrated circuits, it isoften necessary to remove liquids such as water or solvents from thesemiconductor or integrated circuit. For example, the semiconductor maybe exposed to water through contact with aqueous solutions. At least aportion of the water is likely to remain on the semiconductor after thecontacting. Alternatively, water may be formed as a reaction productduring the chip fabrication. For example, U.S. Pat. Nos. 5,858,880 and5,874,367 describe a method of planarizing wafers by forming siliconoxide films on the surface of the wafer by reacting silane with hydrogenperoxide to form silicon hydroxide. The silicon hydroxide polymerizes toform a gel containing water and polymers having the general formulaSi_(x)(OH)_(y) or Si_(x)H_(y)(OH)_(z). More water is formed when thepolymers are annealed to form the final SiO₂ planarizing layer. Thewater is normally removed from the planarized wafer by heating.

Removing water from the wafer by heating can lead to structural problemsin the wafer. For example, when the planarizing silicon hydroxidepolymer gel layer described above is heated and annealed, the layer cancrack if the rate of moisture removal is not controlled carefully duringthe phase transition from a gel to a solid. Controlling the rate ofwater loss can be achieved by careful temperature control, but this isexpensive and time consuming. Alternatively, a silica capping layer canbe formed on top of the wafer to control the rate of moisture release.Processing conditions must be controlled carefully to prevent crackingof the polymer layer. There is a need for more convenient and reliablemethods of removing water during the processing of wafers.

The semiconductor or integrated circuit may also be exposed to solventsduring processing. For example, spin-on layers are formed by spinapplying silicon oxide, with or without dopants, in a solvent. Thesolvent is removed by baking, leaving a planarized SiO₂ layer. The layeris subject to cracking during the drying process while the layerundergoes a phase change into a solid layer. There is a need forimproved methods of removing solvents from semiconductor substrateswithout damaging the wafer.

SUMMARY OF THE INVENTION

One aspect of the invention relates to a method of removing at least aportion of a first liquid from a liquid-containing layer on asemiconductor substrate. The method comprises forming a first layercontaining the first liquid on the semiconductor substrate, contactingthe first layer with a second liquid which attracts the first liquid inthe first layer, and transferring at least a portion of the first liquidfrom the first layer into the second liquid. The method also comprisesseparating the second liquid from the first layer, removing at least aportion of the first liquid from the first layer; and inducing a phasetransition in the first layer. The phase transition may occur during orafter the contacting.

Another embodiment of the invention comprises annealing the substrateand the first layer. Advantageously, the first layer undergoes the phasetransition during the annealing.

Another aspect of the invention relates to a method of isolating pluraltrenches on a substrate. The method comprises placing the substrate in achamber, introducing silicon-containing vapor and hydrogen peroxidevapor into the chamber, and reacting the silicon-containing vapor withthe hydrogen peroxide vapor to form a liquid layer comprisingsilicon-containing oligomers and water on the substrate, where theliquid layer fills at least a portion of the trenches. The method alsocomprises contacting the liquid layer with a hygroscopic liquid toremove at least a portion of the water in the liquid layer, separatingthe hygroscopic liquid from the liquid layer, and heating the liquidlayer to a temperature sufficient to form a solid comprising silica inat least a portion of the trenches.

In one embodiment, the silicon-containing vapor comprises silane. Insome embodiments, the hygroscopic liquid is selected from sulfuric acid,phosphoric acid, and a hygroscopic organic solvent. Advantageously, thehygroscopic liquid comprises sulfuric acid. In an embodiment where thehygroscopic liquid comprises sulfuric acid, the hygroscopic liquidcomprising sulfuric acid is contacted with the liquid layer at atemperature between 0 and 300° Centigrade In another embodiment, thehygroscopic liquid comprising sulfuric acid is contacted with the liquidlayer at a temperature between 100 and 200° Centigrade. In anotherembodiment, the hygroscopic liquid comprising sulfuric acid is contactedwith the liquid layer at a temperature of approximately 150° Centigrade.

In an embodiment of the invention, the hygroscopic liquid comprisingsulfuric acid is at a concentration of between 50 and 98 weight percentsulfuric acid. In another embodiment, the hygroscopic liquid comprisingsulfuric acid is at a concentration of approximately 98 weight percentsulfuric acid.

In an embodiment of the invention, the liquid layer is heated to atemperature between 100 and 1100° Centigrade to form the solidcomprising silica in at least some of the trenches. In anotherembodiment, the liquid layer is heated to a temperature between 300 and800° Centigrade. In yet another embodiment, the liquid layer is heatedto a temperature of approximately 400° Centigrade.

Another aspect of the invention relates to a method of treating asemi-conductor substrate. The method comprises: placing the substrate ina chamber, introducing silicon-containing vapor and hydrogen peroxidevapor into the chamber, reacting the silicon-containing vapor with thehydrogen peroxide vapor to form a liquid layer comprisingsilicon-containing oligomers and water on the substrate, and treatingthe liquid layer with a hygroscopic liquid, thereby removing at least aportion of the water in the liquid layer.

The method may further comprise separating the hygroscopic liquid fromthe liquid layer. In an embodiment of the invention, the method furthercomprises heating the liquid layer after separating the hygroscopicliquid from the liquid layer. Advantageously, the heating forms a solidcomprising silica from the liquid layer.

In an embodiment of the invention, the solid comprising silica forms aninterlayer dielectric layer on the substrate. Advantageously, theinterlayer dielectric layer comprises a trench. The method may furthercomprise filling the trench with a metal. In an embodiment, thesubstrate comprises a plurality of trenches, and the solid comprisingsilica isolates the substrate between the trenches.

In another embodiment, the substrate comprises a plurality of metallines on the substrate, and the solid comprising silica forms adielectric layer over the plurality of metal lines.

In an embodiment of the invention, the silicon-containing vaporcomprises methyl silane, and the liquid layer is heated to a temperaturesufficient to convert the liquid layer to a solid comprising siliconoxide. Advantageously, the solid comprising silicon oxide forms alow-dielectric layer.

Another aspect of the invention concerns a method of treating asemiconductor substrate in a chamber. The method comprises applying afirst liquid comprising silicon and a second liquid onto the substrate.The method further comprises contacting the first liquid comprisingsilicon and the second liquid with a third liquid which attracts thesecond liquid, removing at least a portion of the second liquid; andseparating the third liquid from the first liquid comprising silicon onthe substrate. In an embodiment, the second liquid comprises water andthe third liquid comprises a hygroscopic liquid.

In an embodiment of the invention, the first liquid comprising siliconcomprises silicon dioxide. In another embodiment, the first liquidfurther comprises a dopant selected from the group consisting ofarsenic, antimony, boron, phosphorus, and gallium. In one embodiment,the applying comprises spin applying the first liquid comprising siliconand the second liquid onto the substrate. In another embodiment, theapplying comprises chemical vapor depositing the first liquid comprisingsilicon and the second liquid onto the substrate.

In another embodiment, the applying comprises introducingsilicon-containing vapor and hydrogen peroxide vapor into the chamberand reacting the silicon-containing vapor with the hydrogen peroxidevapor to form the first liquid comprising silicon and the second liquid,where the second liquid comprises water.

Another aspect of the method of the invention concerns a method oftreating a semiconductor substrate in a chamber. The method comprisesapplying a first liquid onto the substrate and heating the substrate andthe first liquid, thereby forming a second liquid and a third liquid.The method also comprises contacting the second liquid and the thirdliquid with a fourth liquid which attracts the third liquid, removing atleast a portion of the second liquid, and separating the fourth liquidfrom the second liquid on the substrate.

In an embodiment of the method of the invention, the applying comprisesspin applying the first liquid onto the substrate. In anotherembodiment, the first liquid comprises a siloxane or an organosiloxane.The third liquid advantageously comprises water, and the fourth liquidcomprises higher oligomers of the siloxane or organosiloxane. The methodmay further comprise annealing the substrate and the fourth liquid,forming a layer comprising silicon dioxide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electron micrograph of a flow filled silicon wafer at amagnification of 1000× after a standard anneal at 400° C.

FIG. 2 is an enlargement of the electron micrograph of the flow filledsilicon wafer of FIG. 1.

FIG. 3 is an electron micrograph of a flow filled silicon wafer at amagnification of 1000×, where the flow filled silicon wafer was dippedin sulfuric acid before annealing at 400° C.

FIG. 4 is an enlargement of the electron micrograph of the flow filledsilicon wafer of FIG. 3.

FIG. 5 is a partial cross-sectional view of a substrate with a pluralityof trenches covered by a liquid layer containing silicon oligomers.

FIG. 6 illustrates the substrate of FIG. 5 after contacting the liquidlayer with a hygroscopic liquid.

FIG. 7 is a partial cross-sectional view of a substrate with metallines, where a liquid layer containing silicon oligomers has beendeposited over the substrate and metal lines.

FIG. 8 is a partial cross-sectional view of a substrate covered with aninterlayer dielectric layer with a trench.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present application describes a method of drying substrates bycontacting the substrate with a hygroscopic liquid. While illustrated inthe context of drying semiconductor substrates after flowfilling thesemiconductor substrate with silicon hydroxide, the skilled artisan willrecognize many other applications for the methods disclosed herein. Inparticular, the method can be used to dry dielectric layers coveringmetallic lines and interlayer dielectric layers.

The method is particularly advantageous when there is a phase change inthe layer which is being dried, either during or after the dryingprocess.

The method is also applicable to removing other liquids such as solventsfrom substrates. When the method is applied to removing other liquids,the substrate is contacted with a liquid which attracts the solvent onthe substrate. The liquid and solvent are then separated from thesubstrate, removing the solvent from the semiconductor substrate. Theapplication therefore broadly relates to a method of removing liquidsfrom a semiconductor substrate by contacting the substrate with a liquidwhich attracts the liquid on the substrate. The method has broadapplication, and the examples below are only illustrative of theapplication of the method.

The invention may be performed in different ways, and a specificembodiment will be described below by way of example. The invention isnot limited to the specific embodiment in the example, and otherexamples will be given.

The need for an improved method of drying substrates was recognized whena previously unrecognized problem was identified during the isolation ofshallow trenches by filling the trenches with a dielectric such assilicon oxide. The trenches can be filled by reacting silane (SiH₄) withhydrogen peroxide (H₂O₂) at −5 to 20° C. to form monosilicic acid,Si(OH)₄, by the FLOWFILL™ process, described in detail in U.S. Pat. Nos.5,858,880 and 5,874,367, herein incorporated by reference. Themonosilicic acid forms a gel which flows into the trench. Themonosilicic acid gel polymerizes to form higher oligomers and water bythe reaction:n Si(OH)₄ →H[OSi(OH)₂]_(n)OH+(n−1)H₂O  (1)

forming a thicker gel. Traditionally, the water is removed from the gelby heating, with or without vacuum. The gel is hardened into anamorphous SiO₂ layer by annealing at high temperature, producing yetmore water by the reaction:H[OSi(OH)_(2]n)OH→n SiO₂ +(n+1) H₂O.  (2)

It was previously known that removing water from the gel by heating cancause cracking of the top of the layer. Heating procedures forminimizing the cracking of the layer are described in the two patentscited above. The heating can be done slowly and/or by forming a siliconoxide capping layer, which acts as a diffusion membrane, controlling therate of drying.

FIG. 1 shows a photomicrograph of a series of trenches filled with SiO₂prepared by the standard method of reacting silane with hydrogenperoxide to form a gel followed by annealing at 400° C. FIG. 2 shows anenlargement of one of the filled trenches of FIG. 1. There are voids atthe bottom of the trench. The presence of the voids is a previouslyunrecognized problem that could lead to poor performance or prematurefailure of the semiconductor due to the density irregularities in thefilled trench.

It has unexpectedly been discovered that formation of the voids in thefilled trenches can be avoided by exposing the gel to a hygroscopicliquid prior to annealing, according to an embodiment of the method ofthe invention.

FIG. 3 shows a photomicrograph of the filled trenches formed bycontacting the gel with sulfuric acid prior to annealing, according toan embodiment of the method of the invention. FIG. 4 shows anenlargement of one of the filled trenches from FIG. 3. In contrast tothe filled trenches formed by the traditional method, there are no voidsat the bottom of the filled trenches when the gel was exposed to ahygroscopic liquid prior to annealing.

It is believed that the voids at the bottom of the filled trenchesformed by the traditional method are caused by evaporation of the waterformed during the oligomerization of monosilicic acid in the gel, asshown in equation (1) above. When the wafer is annealed, the previouslyformed water vaporizes while the oligomers in the gel are simultaneouslydehydroxylated and undergo a phase change to form the solid silica layerand water, as shown in equation (2) above. The solid silicon oxide can'tflow into the voids left by the departing water.

By contrast, when the water-containing silicon oligomer gel is exposedto a hygroscopic liquid in accordance with an embodiment of theinvention, the hygroscopic liquid removes at least a portion of thewater from the gel at low temperature before the wafer and gel areannealed at high temperature. The gel which fills the trench can flow tofill any voids which were formed by the vaporizing water. Far less wateris left in the gel after exposure to the hygroscopic liquid than withthe conventional process. Less water is therefore available to vaporizeduring the annealing process to form voids. Further, it is believed thatthe hygroscopic liquid dehydroxylates the oligomers of monosilicic acidin addition to removing the already-formed water. The dehydroxylation ofthe oligomers means that less water is produced when the silica solid isformed from the gel by a phase transition during annealing, as shown inequation (2) above. The high temperature anneal after drying with thehygroscopic liquid according to an embodiment of the invention istherefore mainly to reflow the silica film rather than to simultaneouslyremove water while reflowing the film, as in the conventional method.

The method of removing water from the semiconductor substrate byexposing the substrate to a hygroscopic liquid is particularlyadvantageous when a phase transition occurs during or after exposure tothe hygroscopic liquid. For example, the water-containing siliconoligomer gel from the FLOWFILL™ process undergoes a phase transitionfrom a fluid gel to a solid during the annealing process. By removingthe water from the fluid gel before the gel undergoes the phasetransition to the solid silica layer, the gel can flow into any voidsformed prior to vaporization of water, and little water remains in thegel to form new voids when the remaining water vaporizes.

The method more generally is applicable to any process where a liquidexists in a material which is flowing. For example, the method can beapplied to layers containing organic solvents or inorganic solventsother than water. By removing liquid from the flowing material with aliquid which attracts the liquid in the flowing material, the solidformed after the phase change of the flowing material often has moreuniform density than the solid formed by conventional technology.

FIG. 5 illustrates the application of the embodiment of the method ofthe invention to shallow trench isolation (STI) in more detail. AlthoughFIG. 5 illustrates a specific embodiment of the method of the invention,the method is not limited to the embodiment illustrated in FIG. 5.

FIG. 5 shows a substrate 10 covered with a liquid-containing layer 30.Although FIG. 3 shows the liquid-containing layer 30 filling a pluralityof trenches 20, the trenches 20 illustrate the embodiment of shallowtrench isolation and are not meant to be limiting on the scope of themethod of the invention.

The substrate 10 may be a semiconductor such as silicon or galliumarsenide, or it may be an insulating layer if Silicon-On Insulator (SOI)or a similar technology is used. For example, the insulator may besapphire, if Silicon-On-Sapphire (SOS) is used. The methods of thepresent invention have broad application to a wide variety of substrates10.

The liquid in the liquid-containing layer 30 can be water or anothersolvent, including, but not limited to, an inorganic solvent or anorganic solvent. Suitable organic solvents include, but are not limitedto, hydrocarbons, chlorinated solvents, alcohols, ethers, aldehydes,ketones, silicones, or any other suitable liquid.

The liquid-containing layer 30 may be applied to the substrate 10 by anysuitable method including spraying, chemical vapor deposition, or thespin-on process.

The liquid-containing layer 30 is contacted with a liquid-attractiveliquid 40, as shown in FIG. 6. The liquid-attractive liquid 40 is chosenso that the liquid in the liquid-containing layer 30 is attracted by theliquid-attractive liquid 40. The liquid-attractive liquid 40 draws atleast a portion of the liquid in the liquid-containing layer 30 into theliquid-attractive liquid 40, as indicated by the arrows in FIG. 6.

If the liquid in the liquid-containing layer 30 is water, theliquid-attractive liquid 40 is preferably a hygroscopic liquid. Suitablehygroscopic liquids include, but are not limited to, sulfuric acid,phosphoric acid, and hygroscopic organic solvents. Anhydrous ethanol isan example of a hygroscopic organic solvent which is suitable for use inthe invention. Sulfuric acid is an exemplary hygroscopic liquid. Thehygroscopic liquid as the liquid-attractive liquid 40 removes at least aportion of the water from the liquid-containing layer 30.

If the hygroscopic liquid is sulfuric acid, the concentration ofsulfuric acid is preferably between 50 and 98 weight percent sulfuricacid, more preferably between 80 and 98 weight percent sulfuric acid,and most preferably approximately 98 weight percent sulfuric acid. Ifthe hygroscopic liquid is phosphoric acid, the concentration ofphosphoric acid is preferably between 70 and 100 weight percentphosphoric acid, more preferably between 75 and 85 weight percentphosphoric acid, and most preferably approximately 85 weight percentphosphoric acid.

The substrate 10 and liquid-containing layer 30 are contacted with thehygroscopic liquid as the liquid-attractive liquid 40 at a temperatureof 0 to 300° C., more preferably between 100 to 200° C., and mostpreferably approximately 150°0 C. The substrate 10 and liquid-containinglayer 30 are contacted with the hygroscopic liquid for a period of 1 to120 minutes, more preferably between 20 and 60 minutes, and mostpreferably for approximately 30 minutes.

If the hygroscopic liquid is an organic solvent, the substrate 10 andliquid-containing layer 30 are contacted with the organic hygroscopicsolvent at a temperature of 1 to 150° C. and most preferablyapproximately 50° C.

The liquid-attractive liquid 40 and the liquid which is attracted fromthe liquid-containing layer 30 are separated from the substrate 10 andliquid-containing layer 30 by any suitable method, for example bytilting the substrate 10 or spin dry.

Another method for separating the liquid-attractive liquid 40 from thesubstrate 10 and liquid-containing layer 30 is by contacting theliquid-attractive liquid 40 with a liquid in which the liquid-attractiveliquid 40 is soluble. The liquid and dissolved liquid-attractive liquid40 can be separated by tilting the substrate 10. If the liquid in whichthe liquid-attractive liquid 40 is soluble is sprayed on the substrate10 and liquid-containing layer 30, the liquid with dissolvedliquid-attractive liquid 40 can simply flow off the substrate 10 andliquid-containing layer 30. In another embodiment, the substrate 10 andliquid-containing layer 30 are dipped into the liquid in which theliquid-attractive liquid 40 is soluble. The liquid-attractive liquid 40dissolves in the liquid in which it is soluble, and the substrate 10 andliquid-containing layer 30 can be lifted out of the liquid, leaving theliquid-attractive liquid 40 behind.

Additional process steps may be performed after removing at least aportion of the liquid from the liquid-containing layer 30 by contactingthe substrate 10 and liquid-containing layer 30 with theliquid-attractive liquid 40 without departing from various embodimentsof the invention. For example, the substrate 10 and liquid-containinglayer 30 may be exposed to reduced pressure and/or heat to remove moreliquid from the liquid-containing layer 30. The substrate 10 andliquid-containing layer 30 may be exposed to plasma. In a preferredembodiment, the substrate 10 and liquid-containing layer 30 are annealedto form a solid layer from the liquid-containing layer 30. The solidlayer formed by annealing the liquid-containing layer 30 aftercontacting with the liquid-attractive liquid 40 often has more uniformdensity than solid layers formed by conventional technology. Otherprocess steps may be performed without departing from variousembodiments of the method of the invention.

The method of removing liquid from a liquid-containing layer 30 on asubstrate 10 by contacting with a liquid-attractive liquid 40 has broadapplication, as will be described in more detail in the examples below.

In the embodiment of isolating trenches with the FLOWFILL™ processdescribed earlier and illustrated in FIGS. 5 and 6, theliquid-containing layer 30 is a planarizing layer formed by reactingsilane (SiH₄) with hydrogen peroxide (H₂O₂) in vapor form in a chamberto form monosilicic acid, Si(OH)₄. The monosilicic acid condenses ontothe surface of the substrate 10 by chemical vapor deposition, flows intothe trenches 20, and spontaneously polymerizes to form a gel containinghigher oligomers and water. The liquid-containing layer 30 formed by theFLOWFILL™ method has low viscosity, and the liquid-containing layer 30fills gaps in the substrate 10 and is generally self leveling, forming aplanarized surface.

The liquid-containing layer 30 formed by reacting silane and hydrogenperoxide is contacted with a hygroscopic liquid as the liquid-attractiveliquid 40 to remove water from the silicon-containing gel. In onepreferred embodiment, the hygroscopic liquid is 98% sulfuric acid.Although the sulfuric acid liquid-attractive liquid 40 may be separatedfrom the liquid-containing layer 30 in various ways, one preferredmethod of separating the sulfuric acid from the liquid-containing layer30 is by rinsing the substrate 10 and liquid-containing layer 30 withwater to dissolve the sulfuric acid. The substrate 10 andliquid-containing layer 30 containing the silicon-containing oligomersare annealed to complete the drying and to dehydroxylate the oligomers,forming silicon oxide and water, as shown in equation (2). The siliconoxide fills at least a portion of the trenches 20, thereby isolating thetrenches 20. The substrate 10 and liquid-containing layer 30 areannealed at a temperature of 100 to 1000° C., more preferably 300 to800° C., and most preferably approximately 400° C. for between 1 and 60minutes, more preferably 10 to 30 minutes, and most preferably 30minutes.

The filled trenches 20 shown in FIGS. 3 and 4 were formed by forming aliquid-containing layer 30 with the FLOWFILL™ process, dipping thesubstrate 10 and liquid-containing layer 30 in 98% sulfuric acid at 150°C. for 30 minutes to remove at least a portion of the water from thegel, dipping the partially dried substrate 10 and liquid-containinglayer 30 in deionized water to remove the sulfuric acid, and annealingthe substrate 10 and liquid-containing layer 30 at 400° C. for 30minutes to form the solid silica which fills the trenches 20. As shownin FIG. 4, there were no voids in the bottom of the filled trenchesformed by the embodiment of the method of the invention, in contrastwith the filled trenches formed by conventional technology.

In another embodiment, the liquid-containing layer 30 is formed on thesubstrate 10 by chemical vapor deposition through a modified form of theFLOWFILL™ process in which methyl silane (CH₃SiH₃) rather than silane isreacted with hydrogen peroxide in the chamber. The liquid-containinglayer 30 on the substrate 10 is contacted with a hygroscopic liquid asthe liquid-attractive liquid 40 to remove water from theliquid-containing layer 30, the liquid-attractive liquid 40 is separatedfrom the liquid-containing layer 30, and the substrate 10 andliquid-containing layer 30 are annealed to form a layer comprisingsilicon oxide, just as in the embodiment of the invention with thetraditional FLOWFILL™ process.

The layer comprising silicon oxide formed from methylsilane and hydrogenperoxide contains silicon-carbon bonds in addition to silicon-oxygenbonds. The silicon oxide layer with silicon-carbon bonds in addition tosilicon-oxygen bonds has a reduced dielectric constant compared to thesilicon oxide layer formed by the normal FLOWFILL™ process. In thisembodiment of the method, a layer with a low dielectric constant isproduced. Low dielectric constant isolation can reduce parasiticcapacitance and cross-talk between devices. The low dielectric layerformed with the embodiment of the method of the invention has moreuniform density than a low dielectric layer formed through conventionalmethods.

In another embodiment, the liquid-containing layer 30 is formed by spinapplying a mixture of silicon dioxide in a liquid onto the substrate 10to form a liquid-containing layer 30 through the spin-on process. Theliquid in the liquid-containing layer 30 formed by the spin-on processmay be water or an organic solvent. Dopants such as arsenic, antimony,boron, phosphorus, and gallium may optionally be included in the liquid.If the liquid in the liquid-containing layer 30 is water, theliquid-containing layer 30 is contacted with a liquid-attractive liquid40 which is a hygroscopic liquid. If the liquid in the liquid-containinglayer 30 is an organic solvent, the liquid-containing layer 30 iscontacted with liquid-attractive liquid 40 which attracts the organicsolvent in the liquid-containing layer 30 formed by the spin-on process.

After the liquid-containing layer 30 formed by the spin-on process iscontacted with the liquid-attractive liquid 40, and the liquidattractive liquid 40 is separated from the liquid-containing layer 30,the substrate 10 and liquid-containing layer 30 formed by the spin-onprocess are annealed to form a layer comprising silicon dioxide. Ifdopants are added to the liquid in the liquid-containing layer 30, thelayer comprising silicon dioxide is doped with the dopant during theannealing.

In another embodiment of the method of the invention with the spin-onprocess, the liquid-containing layer 30 is formed by spin applying aliquid comprising a siloxane or an organosiloxane, either with orwithout an organic solvent. If the liquid-containing layer 30 containsan organic solvent, the liquid-containing layer 30 may be contacted withliquid-attractive liquid 40 which attracts the organic solvent in theliquid-containing layer 30. Ethanol is an example of a suitableliquid-attractive liquid 40 which attracts the organic solvent in theliquid-containing layer 30. After the liquid-containing layer 30 formedby the spin-on process is contacted with the liquid-attractive liquid40, and the liquid attractive liquid 40 is separated from theliquid-containing layer 30, the substrate 10 and remainingliquid-containing layer 30 formed by the spin-on process are annealed toform a layer comprising silicon dioxide.

Alternatively, or, in addition, the liquid-containing layer 30 may beheated prior to annealing to form a liquid-containing layer comprisinghigher oligomers of the siloxanes or organosiloxanes and water. Theliquid-containing layer 30 comprising higher oligomers of the siloxanesor organosiloxanes and water may be contacted with a liquid-attractiveliquid 40 which is a hygroscopic liquid. The hygroscopic liquid removeswater from the liquid-containing layer 30. The liquid-containing layer30 with the higher oligomers of the siloxanes or organosiloxanes isannealed to form a layer comprising silicon dioxide and water. Removingat least a portion of the water in the liquid-containing layer 30 bycontacting the liquid-containing layer 30 with a hygroscopic liquid asthe liquid-attractive liquid 40 produces a layer comprising silicondioxide after annealing which contains fewer voids than if theliquid-containing layer 30 had not been contacted with the hygroscopicliquid.

Another embodiment of the method of the invention is illustrated in FIG.7. A plurality of metal lines 50 are present on the substrate 10. TheFLOWFILL™ process is used to apply silicon oligomers onto the substrate10 and metal lines 50 as the liquid-containing layer 30. Alternatively,the spin-on process is used to apply a silicon dioxide slurry in aliquid as the liquid-containing layer 30 onto the substrate 10 and metallines 50. The liquid-containing layer 30 is contacted with anappropriate liquid-attractive liquid 40, the liquid-attractive liquid 40is separated from the liquid-containing layer 30, and the substrate 10and liquid-containing layer 30 are annealed to produce a dielectricsilicon oxide layer over the metal lines 50 and substrate 10. Thedielectric layer formed by through the embodiment of the method of theinvention has more uniform density than a dielectric layer formed byconventional technology.

Another embodiment of the method is illustrated in FIG. 8. An interlayerdielectric layer 80 of silica is formed on the substrate 10 bydepositing a liquid-containing layer comprising silicon formed by theFLOWFILL™ process or the spin-on process, contacting theliquid-containing layer 30 with the liquid-attractive liquid, separatingthe liquid-attractive liquid 40 from the liquid-containing layer 30, andannealing the substrate 10 and liquid-containing layer 30 to form thesilica interlayer dielectric layer 80. A trench 20 is formed in theinterlayer dielectric layer 20 as shown in FIG. 8. The trench 20 isfilled with metal by the damascene process. The interlayer dielectriclayer 80 formed by the embodiment of the invention has more uniformdensity than a interlayer dielectric layer formed by conventionaltechnology. A uniform interlayer dielectric layer 80 can: 1. insure agood etch profile of the trench; 2. remove all liquid to avoidoutgassing which harms metal; and 3. provide better reliability.

In many applications, layers formed by contacting the liquid-containinglayer 30 with the liquid-attractive liquid 40 to remove liquid from theliquid-containing layer 30 prior or during a phase transition are morehomogeneous than the layers formed by conventional technology.

Various modifications and alterations of this invention will be apparentto those skilled in the art without departing from the scope and spiritof this invention. It should be understood that the invention is notlimited to the embodiments disclosed herein, and that the claims shouldbe interpreted as broadly as the prior art allows.

1. A method of treating a semiconductor substrate in a chamber, themethod comprising: forming a liquid layer containing water on thesemiconductor substrate; contacting the liquid layer with a hygroscopicliquid and transferring at least a portion of the water from the liquidlayer into the hygroscopic liquid; separating the hygroscopic liquidfrom the liquid layer; and inducing a phase transition in the liquidlayer after contacting.
 2. The method of claim 1, wherein inducing aphase transition is conducted by annealing the semiconductor substrateand the liquid layer.
 3. The method of claim 1, wherein the liquid layercomprises silicon and a dopant selected from the group consisting ofarsenic, antimony, boron, phosphorous, and gallium.
 4. The method ofclaim 1, wherein the liquid layer is formed by reactingsilicon-containing vapor with hydrogen peroxide vapor.
 5. The method ofclaim 4, wherein the silicon-containing vapor comprises silane.
 6. Themethod of claim 1, wherein the hygroscopic liquid is selected from thegroup consisting of sulfuric acid, phosphoric acid, and a hygroscopicorganic solvent.
 7. The method of claim 1, wherein the hygroscopicliquid comprises sulfuric acid.
 8. The method of claim 7, wherein thehygroscopic liquid comprising sulfuric acid is contacted with the liquidlayer at a temperature between 0° and 300° Centigrade.
 9. A method oftreating a semiconductor substrate in a chamber, the method comprising:placing the semiconductor substrate in the chamber; forming aliquid-containing layer on the semiconductor substrate; contacting theliquid-containing layer with a liquid-attractive liquid, therebyremoving at least a portion of liquid in the liquid-containing layerinto the liquid-attractive liquid; and separating the liquid-attractiveliquid from the liquid-containing layer after contacting.
 10. The methodof claim 9, wherein the liquid in the liquid-containing layer is waterand the liquid-attractive liquid is a hygroscopic liquid.
 11. The methodof claim 10, wherein the hygroscopic liquid is selected from the groupconsisting of sulfuric acid, phosphoric acid, and hygroscopic organicsolvents.
 12. The method of claim 11, wherein the hygroscopic liquid issulfuric acid having a concentration of 50 to 98 weight percent sulfuricacid.
 13. The method of claim 9, wherein the liquid-attractive liquid isseparated from the liquid-containing layer by tilting the semiconductorsubstrate.
 14. The method of claim 9, wherein the liquid-attractiveliquid is separated from the liquid-containing layer by spinning dry thesemiconductor substrate.
 15. The method of claim 9, wherein theliquid-attractive liquid is separated from the liquid-containing layerby contacting the liquid-attractive liquid with a separating liquid inwhich the liquid-attractive liquid is soluble.
 16. A method of treatinga semiconductor substrate, comprising: applying a liquid-containinglayer to the substrate, wherein the liquid-containing layer is formed byreacting a silicon-containing vapor with hydrogen peroxide vapor;contacting the liquid-containing layer with a hygroscopic liquid toremove at least a portion of water from the liquid-containing layer; andseparating the hygroscopic liquid from the liquid-containing layer. 17.The method of claim 16, wherein the separating is performed by rinsingthe substrate and liquid-containing layer with water.
 18. The method ofclaim 16, further comprising annealing the substrate andliquid-containing layer after separating.
 19. The method of claim 18,wherein the substrate and liquid-containing layer are heated afterseparating and prior to annealing.
 20. The method of claim 16, whereinthe liquid-containing layer is formed on the substrate by chemical vapordeposition.